In the adsorption desulfurization for hydrocarbons, the sulfur element in the hydrocarbon feedstock is fixed, e.g. by converting the sulfur element in sulfur containing hydrocarbons to zinc sulfide. By passing oxygen to the regenerator and combusting therein, zinc sulfide in the catalyst particles and oxygen are reacted to form zinc oxide and sulfur dioxide, and therefore the adsorption activity of the catalyst is recovered.
Because the sulfur element has a larger atom radius than the oxygen element, therefore in the reaction-regeneration cycle, it is inevitable that the crystal lattice of the catalyst changes and even the crushing of catalyst particles may occur, resulting in the formation of catalyst fine powder. In addition, in the multiphase fluidized bed reactor, the reaction gas and the catalyst are contacted with each other. Under the action of the reaction stream, the catalyst is kept in a fluidized state. After the long term collision and abrasion among catalyst particles, the crushing will occur, which also results in the formation of catalyst fine powder.
The current S-Zorb adsorption desulfurization process uses the fluidized adsorption reactor. The reaction product leaves the reactor through a dust filter located on the top of the reactor, and the solid particles leave the reactor through a discharging tube located below the reaction stream in the upper bed of the reactor and enter the regenerator and then the reducer for regeneration and reduction. In the fluidized absorption reactor, the powder in the catalyst and the powder formed by the long-term abrasion of catalyst particles are raised up to the settling space of the reactor and kept in suspension for long period. The suspended powder and particles have no chance to return to the dense bed of the reactor or to be discharged from the reactor, and therefore will have an effluence on the stable run of the apparatus.
In the existing adsorption desulfurization apparatus for the catalytic gasoline, a built-in metal filter is generally used to recover the catalyst. However, the metal filter has a small pore diameter and mainly recovers the superfine catalyst powder. The solid particles having a size of e.g. greater than 2 μm is prone to remain in the reaction system, resulting in that a large amount of catalyst fine powder with a smaller particle size cannot be duly removed from the reactor, and therefore the desulfurization effect and the normal operation are impacted.
The catalyst for adsorption desulfurization has a lower mechanical strength than other solid catalysts. Where a conventional cyclone separator is provided in the adsorption desulfurization reactor to separate the catalyst, due to the high gas flow rate in the cyclone separator, upon separating the hydrocarbon product from catalyst particles, there will be intense collision among particles and between the particles and the cyclone separator's walls, which is prone to cause the crushing of the catalyst. Moreover, there is a centrifugal force field with high turbulent flow in the cyclone separator. Various size particles have different turbulent flow strengths. This results in that the catalyst fine powder in the fluidized bed reactor cannot be effectively separated and sorted out. Furthermore, due to the substantive crushing of catalyst, the quantity of the catalyst fine powder in the fluidized bed reactor increases, and therefore the catalyst consumes faster. Therefore, in general, the cyclone separator is not chosen as a component for separating and sorting the catalyst in adsorption desulfurization reactor.
Therefore, it is urgent to provide a new adsorption desulfurization reaction apparatus, which can not only accomplish the adsorption desulfurization and the regeneration and reduction of the catalyst, but also can duly remove the fine catalyst powder formed in the system from the reaction system to ensure the desulfurization effect, and accomplish stable and long-term run of the apparatus. Moreover, when separating and sorting the catalyst particles, it is required that no or substantially no secondary crushing of catalyst particles appears. Based on this, it still needs a sorter that can effectively separate solid particles with larger size from a gas stream entraining solid particles, and will not exacerbate the crushing of catalyst particles.